This invention relates to a surgical instrument for use in endoscopic procedures and, in particular, to a trocar assembly having improved adapter seals for accommodating differently sized surgical instruments.
Trocars are surgical instruments that have found wide application in many types of procedures where puncture-type incisions are to be made; in particular, insufflatory surgery. Insufflatory surgery involves filling a body cavity with a pressurized gas to maintain the cavity under a certain pre-determined pressure. In such surgery, a trocar is used to puncture the body cavity by inserting the trocar through a cannula or sheath. After the incision is made by the trocar, the cannula is partially inserted into the body cavity through the incision. The trocar is then removed from the cannula, and thereafter, other surgical instruments may be inserted through the cannula to perform various endoscopic procedures. A trocar assembly is a unit typically comprising a trocar and a cannula. Trocar assemblies are available as disposable or reusable units.
Due to the minimal invasive nature of endoscopic procedures, endoscopy is a preferred surgical approach when possible. Endoscopic surgical procedures employ a variety of surgical instruments, e.g., endoscopes, biopsy forceps, bipolar forceps, coagulation probes, etc. These surgical instruments differ in shape and size. For example, in the course of a single surgical procedure, some of the instruments used may have a cross-sectional diameter in their elongate regions on the order of 5 mm, while others may have a diameter of 10 mm or larger. The shape of the operative end of the instruments will also vary depending on their intended function. A gas-tight seal between the cannula and an instrument inserted therein must be maintained. A typical cannula assembly will have a flexible seal ring as a sealing means. The flexible seal ring allows instruments within a certain range of sizes to be inserted into the cannula and provides a seal with those instruments to prevent gas leakage. It is desirable to avoid removing a cannula once it has been inserted into the body, however the flexible seal ring may not be able to accommodate the various instruments to be used in performing a surgical procedure. In such cases, cannula assemblies of different sizes may be needed to accommodate the instruments. Commercially available trocar assemblies come in a range of inner diameters (e.g., 3, 5, 7, 8, 10, 11 and 12 mm sizes).
The problem of accommodating instruments of various sizes during a surgical procedure, without replacing cannulas, still remains to be addressed. Large diameter instruments simply cannot be used with a cannula having a smaller diameter. Small diameter instruments, e.g., 3 mm, are unusable in a larger size cannula, e.g., 12 mm, because the flexible seal ring in the cannula assembly is too large and cannot effectively maintain the gas pressure within the body cavity. The trocar and cannula assemblies now available for maintaining a certain gas pressure in the cavity when using differently sized surgical instruments are simply too difficult and inconvenient to use.